An oblique view of the structure of an existing terminal plug for an electronic device (a timer) is shown in FIG. 5. The terminal plug of this timer comprises resin thermoplastic base 73; key boss 71, which protrudes from the center of the front surface of the base; number of through-holes 72, which are arranged in a circle around the outer perimeter of the key boss; a number of metal pins 74, which are inserted in through-holes 72; and copper-clad laminate 75 (circuit pattern 75a), which is glued to the back of base 73. The base of each metal pin 74 is soldered to its corresponding pattern 75a on copper-clad laminate 75. To ensure isolation, base 73 has a slit 76 between every two pins 74. Each connector terminal 75b of these circuit patterns 75a is connected to a circuit pattern connector 78 on the inner surface of the upper and lower walls (77a and b) of the casing 77 which is assembled with base 73.
In existing terminal plugs for electronic devices (timers and so on), metal pins are insertion-molded into the base, and the base of each pin is soldered to the circuit pattern formed on a copper-clad laminate glued to the back of the base. As a result, a large number of components and assembly processes are needed. This has caused a sharp rise in production costs. Using insertion-molding is disadvantageous not only because of the high cost of the components, but also because of the high start-up costs associated with component production. Furthermore, in a terminal plug like that used in a timer, which has eleven poles (and eleven pins), it is difficult to provide isolation between every two pins. More specifically, it is difficult with this type of terminal plug to meet strict standards for isolation distance such as that specified by the VDE (The German Association of Electrical Engineers).